Intel Do-It-Yourself ChallengeOpenCV

Nicolas Vaillietwww.Intel-Software-Academic-Program.com

paul.guermonprez@intel.comIntel Software

2014-02-01

OpenCV ?

Open Computer VisionOpenCV is a well known computer vision library,written in C++. Intel Galileo support this library.If you connect a camera or upload pictures on your board, you can analyze or modify images.

Fast development cycleYou can code and compile on your workstation,run your software at full speed, as often as you wantthen compile for Galileo and validate on the board.

OpenCV BW Sample

Procedure

ToolchainWe assume here you just did the procedure about building the cross compile toolchain and you are able to compile with ${CC} or ${CXX}.

SourceCreate a file named hellocv.cpp and copy/paste the code from the next slide. Save the file.This piece of code comes from OpenCV Tutorials.We encourage you to visit and read quickly all tutorials to have the best panorama view of what OpenCV can do for you.http://docs.opencv.org/doc/tutorials/tutorials.html

Source Code#include <cv.h>#include <highgui.h>

using namespace cv;

int main( int argc, char** argv ) {

char* imageName = argv[1]; Mat image; image = imread( imageName, 1 );

if( argc != 2 || !image.data ) { printf( " No image data \n " ); return -1; }

Mat gray_image; cvtColor( image, gray_image, CV_BGR2GRAY ); imwrite( “reslut.jpg", gray_image );return 0;

}

Compiling and linkingCompile for GalileoCompile and link your program with the following command:${CXX} hellocv.cpp `pkg-config opencv --cflags --libs` -o hellocv

Can’t execute the binary locallyYou cannot run your program on your workstation as it is not compatible with your OS : libraries are linked as if they were on your board, not the way they are in your OS.Try : ldd hellocvYou see some libraries missing ….

Transfer, execute

Transfer and connectscp hellocv root@192.168.xx.xx:~ssh root@192.168.xx.xxchmod +x hellocv

Download sample image, execute, get result imagewget http://docs.opencv.org/_images/Hough_Lines_Tutorial_Original_Image.jpg –O pic1.jpg./hellocv pic1.jpglogout # going back to your workstationscp root@192.168.xx.xx:~/result.jpg .# open the result.jpg file to see the results

Input, Output

Note about graphical components

Forward GUISome OpenCV samples are not command line only as they use the highgui library. You may want to forward the graphical calls to your workstation using the –X flag for ssh.

Disable GUIAnother solution is to modify the code to remove all highgui calls and make the software headless.

OpenCV Sobel Sample

Processing Sobel Derivatives#include "opencv2/imgproc/imgproc.hpp" #include "opencv2/highgui/highgui.hpp" #include <stdlib.h> #include <time.h>#include <stdio.h>

using namespace cv;

int main( int argc, char** argv ) { Mat src, src_gray; Mat grad; int scale = 1; int delta = 0; int ddepth = CV_16S; int c; src = imread( argv[1] ); if( !src.data ) { return -1; }

clock_t tStart = clock();

GaussianBlur( src, src, Size(3,3), 0, 0, BORDER_DEFAULT ); cvtColor( src, src_gray, CV_RGB2GRAY );Mat grad_x, grad_y; Mat abs_grad_x, abs_grad_y; Sobel( src_gray, grad_x, ddepth, 1, 0, 3, scale, delta, BORDER_DEFAULT ); convertScaleAbs( grad_x, abs_grad_x ); Sobel( src_gray, grad_y, ddepth, 0, 1, 3, scale, delta, BORDER_DEFAULT ); convertScaleAbs( grad_y, abs_grad_y );addWeighted( abs_grad_x, 0.5, abs_grad_y, 0.5, 0, grad );

printf(“Time taken: %.3fs\n”, (double)(clock()-tStart)/CLOCKS_PER_SEC);imwrite(“result.jpg”,grad);return 0;}

Sobel derivatives is composed by :- A Gaussian blur- A grayscale conversion- Computer derivatives along X and Y- Adding the two components together

Input, Output, Size, Time

512 x 512 px0.57 secondes

Input, Output, Size, Time

1920 x 1200 px5.18 secondes

Input, Output, Size, Time

300 x 200 px0.12 secondes

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